Not seeing a forum yet for information about these new weapons as well as some tracking of augments folks are getting, etc.
These weapons will drop from Skirmish in either Cirdas Caverns or Rala Waterways and will be augmented via Ghastly Stone / Ghastly Stone +1 / Ghastly Stone +2; which are obtained from skirmish or purchased via Obsidian Fragments @ Divainy-Gamainy Western Adoulin (J-10) when Inventors' Coalition has been edified with an Emblem.
100 O.Frags
1,000 O.Frags
9,800 O.Frags
You obtain O.Frags from participating in skirmish, the amount you received I believe is not only based on performance but also which tier of the Head, Legs, Feet (Simulacrum Segment) traded as the entry requirement for skirmish. Also the higher tier items used for entry will net more drops and increased chances of +1 and +2 stones.
*Reports have O.Frags has been in the avg range of ~300 per event. The augmenting system with stones has a large range between NQ-HQ2 which overlap each other. The long investment of gil and time for these formidable weapons will be great but possibly worth it for those who find more benefit taking skirmish path as opposed to REM.